Inositol phosphates induce DAPI fluorescence shift

The polymer inorganic polyphosphate (polyP) and inositol phosphates, such as phytic acid (IP6), share many biophysical features. These similarities must be attributed to the phosphate groups present in these molecules. Given the ability of polyP to modify the excitation-emission spectra of DAPI (4',6-diamidino-2-phenylindole) we decided to investigate if inositol phosphates possess the same property. We discovered that DAPI-IP6 complexes emit at around 550 nm when excited with light of wavelength 410-420 nm. Inositol pentakisphosphate (IP5) is also able to induce a similar shift in DAPI fluorescence. Conversely, inositol trisphosphates (IP3) and inositol tetrakisphosphates (IP4) are unable to shift DAPI fluorescence. We have employed this newly discovered feature of DAPI to study the enzymatic activity of the inositol polyphosphate multikinase and to monitor phytase phosphatase reactions. Finally, we used DAPI-IP6 fluorescence to determine the amount of IP6 in plant seeds. Using an IP6 standard curve this straight forward analysis revealed that among the samples tested, borlotti beans possess the highest level of IP6 (9.4 mg/gr) while the Indian urad bean the lowest (3.2 mg/gr) The newly identified fluorescence properties of DAPI-IP5 and DAPI-IP6 complexes allow the levels and enzymatic conversion of these two important messengers to be rapidly and reliably monitored.

Source: BJ Signal - March 26, 2014 Category: Biochemistry Authors: B Kolozsvari, F Parisi, A Saiardi Tags: BJ ChemBio Source Type: research